Process development of ready-to-eat custard cream filled chinese steamed bun

Chinese steamed bun is a popular food in Asia. Its storage life is short as it is a high moisture food (HMF). Freezing is a good preservation method, however energy consumption is high. The objective of this study was to develop ready-to-eat custard cream filled Chinese steamed bun (CCSB) with shelf-life of at least 10 days by using hurdle technology. The hurdle parameters used were aw, pH, and modified atmosphere packaging (MAP). The effects of adding glycerol and fructose in custard cream filling and glycerol and lactic acid in Chinese steamed bun were studied by 3x3 factorial design experiment and response surface methodology using preference test on sweetness, texture, and overall acceptance (OAA) for the custard cream and appearance, flavour, texture, and OAA for Chinese steamed bun. It was found that optimum condition for custard cream filling was the addition of 6% glycerol and fructose each, which could reduce aw to 0.915 and the best condition for Chinese steamed bun was the addition of 2.5% glycerol and 0.25% lactic acid, which could reduce aw and pH to 0.912 and 5.78, respectively. From shelf-life study of Chinese steamed bun, the aerobic plate count (AC), aw, and pH of control and hurdle treated products (HP) at different levels of calcium propionate (CaP), packed in PVDC pouch and stored at 302OC, were investigated every 2 days. The results showed that HP without CaP can be stored for at least 16 days similar to HP with CaP and aw increased slightly while pH did not change. From textural measurement by texturometer and sensory evaluation (OAA) of HP without CaP compared with control sample, it was found that shelf-life of this product can be extended to 8 days without the detection of difference by panelists. The shelf-life study of hurdle treated CCSB by MAP using oxygen absorber (OA) showed that CCSB with OA can be stored for 10 days while CCSB without OA can be stored only for 4 days based on microbiological test. However, from textural measurement and predicted OAA score the shelf-life of CCSB with OA was 8 days.